March 21 (HealthDay News) -- Because sleep deprivation may give rise to sleepwalking, it can also help specialists diagnose the condition, say Canadian researchers.

They studied 40 patients referred to a sleep disorder clinic for treatment of suspected sleepwalking.

The patients were examined and spent one night of baseline sleep in the lab. They did their normal activities the next day and returned to the sleep lab in the evening. On the second night, the patients were prevented from falling asleep. They were allowed to have a recovery sleep the next morning, after being awake for 25 hours.

The patients were videotaped during their sleep sessions so that the researchers could evaluate behavioral movements -- such as playing with bed sheets or getting up from the bed -- linked with sleepwalking episodes.

During the baseline sleep session, 32 behavioral episodes were noted in 20 sleepwalkers (50 percent), compared with 92 episodes in 36 patients (90 percent) during recovery sleep.

The researchers found that sleep deprivation also significantly increased the percentage of patients who experienced at least one complex episode.

"By yielding a greater number of episodes with a wide range of complexity, sleep deprivation can facilitate the video-polysomnographically-based diagnosis of somnambulism (sleepwalking) and its differentiation from other disorders," wrote Antonio Zadra, of the University of Montreal, and colleagues.

The study appears in the journal Annals of Neurology.

Observing behavioral events in the sleep lab following sleep deprivation isn't always sufficient to confirm a diagnosis of sleepwalking, the researchers noted. However, when it's used "as a diagnostic tool, sleep deprivation shows a high sensitivity for somnambulism and may be clinically useful with a wider range of somnambulistic patients than previously reported."

Sleepwalking, which affects up to four percent of adults, usually involves misperception and unresponsiveness to surroundings, and mental confusion and amnesia about sleepwalking episodes. There is no proven method of diagnosing sleepwalking, so the disorder is diagnosed on the basis of a patient's clinical history.

The study authors said their findings support recommendations that sleepwalkers should maintain a regular sleep schedule and avoid sleep deprivation.

SOURCE: Annals of Neurology, news release, March 19, 2008